Hi all
Sorry for my bad english.
I own a Kobo Aura 2ndEdv1. I used to download epubs from several Internet sources, and to build some epubs from InDesign documents.
Then I copy them from my PC to the root of Kobo plugged in by USB.
Until last Saturday, all was fine : when I unplugged (by ejecting cleanly) Kobo device, the notication "Importing content (in French Importation du contenu)" was displayed during 1 or 2 seconds, then new books appeared immediatly, even when I added several books.
But since 3 days, importing content became very very very slow, about 10 or 15 minutes for only one book (< 1 Mo). It is also 10 to 15 minutes for 10 ebooks for example.
So I have resetted Kobo to factory parameters. But no change.

Then I also resetted Kobo to default parameters. No more change. Content importing is always so slow.

I'm very annoyed because I have to build many epubs from Indesign documents. I am able to export from InDesign to epubs, but then I have to check them on various devices, particularly Kobo. If I have to wait 15 minutes everytime, I'll became crazy.
Kobo's firmware is currently v4.21.15015.
I attempted to downgrade to v4.19.14123 : I downloaded kobo-update-4.19.14123.zip from pgaskin.net/KoboStuff/, then I plugged (usb) Kobo and copied the whole zip's content to /.kobo and rebooted Kobo. But nothing happens. When rebooted then plugged, /.kobo directory does no more contains files I had copied. And FW version is still v4.21.15015
So I have 2 questions :
1) have you heard of such a slow content import ?
2) what can I do ? and particularly how to downgrade FW ?
Big thanks to you who will

me